Pd-catalyzed C3-selective allylation of indoles with allyl alcohols promoted by triethylborane

Under palladium catalysis, Et3B nicely promotes allyl alcohols to undergo C3-selective allylation of indoles and tryptophan; the yields range 75-95%.     

Pd(0)-catalyzed amphiphilic activation of bis-allyl alcohol and ether

Pd(0).Et3B catalyzes amphiphilic activation of symmetric allylic diol 1 to promote electrophilic allylation at the alpha-position of aldehydes and nucleophilic allylation at the aldehyde CO, furnishing 3-methylenecyclopentalols 2 and thus generation of a zwitterionic trimethylenemethane species from the commercially available diol 1.     

Visible‐Light‐Induced Morphological Changes of Giant Vesicles by Photoisomerization of a Ruthenium Aqua Complex

Visible‐ and red‐light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal‐ 2 : [Ru(C₁₀tpy)(C₁₀pyqu)OH₂]²⁺, C₁₀tpy=4′‐decyloxy‐2,2′;6′,2“‐terpyridine, C₁₀pyqu=2‐[2′‐(6′‐decyloxy)‐pyridyl]quinoline). The ruthenium complex of proximal‐ 2 with closed alkyl chain geometry and a cylinder‐like molecular shape exhibited photoisomerization to distal‐ 2 with an open alkyl chain geometry and a cone‐like shape, both in an aqueous solution and in vesicle dispersions. We observed that light irradiation of giant vesicles containing proximal‐ 2 induced diverse morphological changes.     

Development characteristics of drag-reducing surfactant solution flow in a duct

Development characteristics of dilute cationic surfactant solution flow have been studied through the measurements of the time characteristics of surfactant solution by birefringence experiments and of the streamwise mean velocity profiles of surfactant solution duct flow by a laser Doppler velocimetry system. For both experiments, the concentration of cationic surfactant (oleylbishydroxymethylethylammonium chloride: Ethoquad O/12) was kept constant at 1000 ppm and the molar ratio of the counter ion of sodium salicylate to the surfactants was at 1.5. From the birefringence experiments, dilute surfactant solution shows very long retardation time corresponding to micellar shear induced structure formation. This causes very slow flow development of surfactant solution in a duct. Even at the end of the test section with the distance of 112 times of hydraulic diameter form the inlet, the flow is not fully developed but still has the developing boundary layer characteristics on the duct wall. From the time characteristics and the boundary layer development, it is concluded that the entry length of 1000 to 2000 times hydraulic diameter is required for fully developed surfactant solution flow.List of abbreviations and symbols A₁, A₂ Coefficients for time constant fitting [-] - B Breadth of the test duct [m] - C₁, C₂ Coefficients for time constant fitting [-] - D Pipe diameter [m] - D_H Hydraulic diameter [m] - g Impulse response function [Pa] - H Width of the test duct [m] - n Index of Bird-Carreau model [-] - Re Reynolds number (=U_mD_H/) - Re_D Pipe Reynolds number (=U_mD/) - Re_x Streamwise distance Reynolds number (=U₀x/) - T Absolute temperature [K] - t Time [s] - t_a Retardation time [s] - t_b Build-up time [s] - t_x Relaxation time [s] - t_x1, t_x2 Relaxation time for double time constant fitting [s] - t Time constant in Bird-Carreau model [s] - U Time mean velocity [m/s] - U_m Bulk mean velocity [m/s] - U_max Maximum velocity in a pipe [m/s] - U₀ Main flow velocity [m/s] - u Friction velocity [m/s] - x, y Coordinates [m] - Shear rate [s^–1] - Mean shear rate [s^–1] - n Birefringence [-] - 99% boundary layer thickness [m] - Solution viscosity [Pa·s] - _P, _S Surfactant and solvent viscosity [Pa·s] - ₀, Zero and infinite viscosity of Bird-Carreau model [Pa·s] - Characteristic time in Maxwell model [s] - Water kinematic viscosity [m²/s] - Density [kg/m³] - Solution shear stress [Pa] - _P, _S Surfactant and solvent shear stress [Pa] - Time in convolution [s]     

Rheological characteristics of trimethylolethane hydrate slurry treated with drag-reducing surfactants

Rheological characteristics of trimethylolethane (TME) clathrate–hydrate slurry treated with drag-reducing surfactants were investigated. Friction coefficients and apparent viscosities were measured when the concentration of TME and its hydrate fraction treated with and without drag-reducing surfactants were changed in several steps. From the results, it is found that the surfactant addition causes effective drag reduction in a pipe flow when the hydrate fraction becomes high, while effective drag reduction disappears in the cases of low hydrate fraction. The results of viscosity measurements indicate that the TME molecules disturb the formation of shear-induced structures (SIS) causing drag reduction phenomena. To investigate this interaction between TME and surfactant micelles, the effect of TME concentration on viscosity and relaxation time of solutions was discussed. From this, it was found out that there exists a critical concentration of TME on the formation of SIS and that it becomes larger as shear rate increases. Thus, we conclude that this interaction between TME and micellar structures causes less drag reduction for the cases of low hydrate fraction, while the drag reduction appears in cases of high hydrate fraction because TME concentration in liquid phase becomes small.     

Molecular dynamics simulation of the mixed anion glasses Li4SiO4---Li3BO3

The structure and the mixed anion effect in the conductivity have been examined for the mixed anion glasses Li₄SiO₄---Li₃BO₃ by molecular dynamics (MD) simulation and X-ray diffraction (XRD) analysis. Structure factors derived from the MD simulation are in good agreement with those from derived from the XRD analysis of the actual glasses, showing that the MD simulation successfully reproduces the actual glass structure. Moreover, the enhancement of the diffusion coefficients of the Li⁺ ions in the middle of the composition range in the system Li₄SiO₄---Li₃BO₃ is simulated by the MD calculation. Structural analysis of the glasses derived from the MD simulation revealed that the increase in the halfwidth of the modified radial distribution function of the Li---O pairs due to the mixing of two ortho-oxoanions is one of the factors in the origin of the mixed anion effect in the conductivity.     

Alkyne as a spectator ligand for the nickel-catalyzed multicomponent connection reaction of diphenylzinc, 1,3-butadiene, aldehydes, and amines

Under nickel catalysis, in the presence of 3-hexyne, the aldimines of aromatic amines react with Ph2Zn and one molecule of butadiene to provide 1 exclusively, while the aldimines of aliphatic amines react with Ph2Zn and two molecules of butadiene to provide 2 exclusively, where 3-hexyne serves as a spectator ligand controlling the selective formation of 1 and 2.     

Syntheses, characterization, and photochemical properties of amidate-bridged Pt(bpy) dimers tethered to Ru(bpy)3(2+) derivatives

Amidate-bridged diplatinum(II) entities [Pt(2)(bpy)(2)(μ-amidato)(2)](2+) (amidate = pivalamidate and/or benzamidate; bpy = 2,2'-bipyridine) were covalently linked to one or two Ru(bpy)(3)(2+)-type derivatives. An amide group was introduced at the periphery of Ru(bpy)(3)(2+) derivatives to give metalloamide precursors [Ru(bpy)(2)(BnH)](2+) (abbreviated as RuBnH, n = 1 and 2), where deprotonation of amide BnH affords the corresponding amidate Bn, B1H = 4-(4-carbamoylphenyl)-2,2'-bipyridine, and B2H = ethyl 4'-[N-(4-carbamoylphenyl)carbamoyl]-2,2'-bipyridine-4-carboxylate. From a 1:1:1 reaction of [Pt(2)(bpy)(2)(μ-OH)(2)](NO(3))(2), RuBnH, and pivalamide, trinuclear complexes [Pt(2)(bpy)(2)(μ-RuBn)(μ-pivalamidato)](4+) (abbreviated as RuBn-Pt(2)) were isolated and characterized. Tetranuclear complexes [Pt(2)(bpy)(2)(μ-RuBn)(2)](6+) (abbreviated as (RuBn)(2)-Pt(2)) were separately prepared and characterized in detail. The quenching of the triplet excited state of the Ru(bpy)(3)(2+) derivative (i.e., Ru*(bpy)(3)(2+)) upon tethering the Pt(2)(bpy)(2)(μ-amidato)(2)(2+) moiety is strongly enhanced in RuB1-Pt(2) and (RuB1)(2)-Pt(2), while it is only slightly enhanced in RuB2-Pt(2) and (RuB2)(2)-Pt(2). These are partly explained by the driving forces for the electron transfer from the Ru*(bpy)(3)(2+) moiety to the Pt(2)(bpy)(2)(μ-amidato)(2)(2+) moiety (ΔG°(ET)); the ΔG°(ET) values for RuB1-Pt(2), (RuB1)(2)-Pt(2), RuB2-Pt(2), and (RuB2)(2)-Pt(2) are estimated as -0.01, 0.00, +0.22, and +0.28 eV, respectively. The considerable difference in the photochemical properties of the B1- and B2-bridged systems were further examined based on the emission decay and transient absorption measurements, which gave results consistent with the above conclusions.